Centrifugal switch



Aug. 10, 1948.

' v. H. HARDY CENTRIFUGAL SWITCH Filed June 26, 1944 3noentor away/56rd Gttomegi Patented Aug. 10, 1948 CENTBIFUGAL SWITCH Vaughn H. Hardy, Rochester, N. Y., aslignor to General Mutt)" Corporation, Detroit, Mich., a

corporation of Delaware Application June 26, 1944, Serial No. 2,12%

1 Claims.

This invention relates to the construction of a centrifugal switch which is of general use but designed particularly as an overspeed cutout to short circuit an engine ignition system if the {engine speed exceeds some predetermined safe imit.

One object of the invention is to provide a centrifugal switch that is relatively simple in construction and reliable in operation.

A further object is to provide a holding magnet for the centrifugally operated member of a switch or other centrifugal device to obtain substantially a snap action movement of this member and permit an accurate calibration of the speed at which this member will operate.

Other objects and the advantages of the present invention will be apparent from the following description of the embodiment thereof which is illustrated in the accompanying drawings.

Fig. l is substantially a vertical section of the centrifugal switch assembly.

Fig. 2 is an end elevation on line 2-2 of Fig. 1 with parts broken away.

Fig. 3 is a fragmentary detail view taken substantially on line 3-3 of Fig. 1.

Fig. 4 is a fragmentary detail view with parts in elevation and parts in section substantially on line 4-4 of Fig. 3.

In the embodiment shown herein, the switch is adapted for use as an overspeed cutout to short-circuit an engine ignition system if the engine speed exceeds some predetermined safe limit but it will be understood that certain features of the present invention are adapted for use in other types of centrifugal switches or centrifugally operated devices, of a general nature.

In the drawings, a shaft 6 is shown as mounted by means of ball bearings 8 with shaft sealing means ID in a base l2 with a gear l4 secured to the outer end of the shaft 6. This gear 14 is adapted to be driven by the engine to' rotate the shaft 6 in accordance with engine speed.

The shaft 6 is providedwith an axial bore at its inner end with a bushing Hi to slidably receive a plunger indicated generally at iii. A spring 20 which is housed within the plunger is interposed between the plunger and shaft to urge the plunger axially outward from the bushing 18.

The plunger i8 is provided with an enlarged end face 22 and with an annular shoulder 24 inwardly of this face which is adapted to cooperate with a centrifugally operated latch mechanism to normally retain the plunger in a retracted position against the pressure exerted by the spring 20.

2 The centrifugally operated latch mechanism includes a latch 28 secured to one end of a spring permanent magnet 22 which is generally of 0- shape and preferably of Alnico or other similar magnetic material. The magnet 32 may be secured. within the shaft recess by means of silver solder or the like which is placed in a groove formed between the shaft and magnet as indicated at 34.

As shown particularly in Figs. 3 and 4, the en-- larged portion of the shaft 6 which receives the permanent magnet is cut away adjacent the side to which the reed 28 is secured so that the ends of the magnet constituting the poles thereof extend slightly above or beyond the adjacent portions of the shaft. Secured to the spring reed 28 at each side of the latch 28 or constituting lateral extensions of the latch is an armature 36 which isadapted to contact the poles of the permanent magnet 32 when the latch 28 is in latching engagement with the shoulder 24 of the plunger l8. The armature and latch may be secured to the end of the spring reedv2a by rivets which also secure an upper plate 38 on the opposite side of the reed.

A plurality of contacts, of which only one is shown at 40, are adapted to be'engaged by the end face 22 of plunger l8 when the latch 28 is released and the plunger forced outwardly by spring 20. Each of the contacts such as 40 may be secured by a spring arm 42 with backing plate 44 to a supporting plate 48 of insulating material by means such as the bolt 48 with the spring arms extending radially inward from the connection to the plate to position the several contacts in spaced relation to one another adjacent the center of the plate in the path of the face 22 of the plunger l8.

Alth'ough but a single contact mounting has been shown herein, the present device is provided with three contacts which are equally spaced as indicated by the reinforcing ribs 50 on the plate 46 which are shown in Fig. 2 together with two of the contact mounting bolts 48. In the present switch unit, two of these contacts are adapted to be connected to the ignition system of the engine such as to the magneto primary windings with the third contact connected by a ground strap 52, as shown in Fig. 2, to one of several bolts or screws, such as indicated at 54, which secure the plate 48 to a flange on a switch housing 56 which is in turn secured to the base 12. A cover lit for the end of the switch housing 56 is secured in spaced relation to the plate 8.

with the face 22 of plunger l8 to return the plunger to its retracted position when the push button is manually forced inwardly against the tension of a spring 66 which normally holds the reset member in its outermost position.

It will be apparent from the foregoing description that on rotation of the shaft 6 and the parts mounted thereon, there will be a tendency for the latch 26 to move outwardly because of the centrifugal force which is opposed by the spring tension exerted by the reed 28, the slight friction between the latch 26 and the shoulder 2 4 of the spring-pressed plunger [8, and the magnetic force tending to hold the armature 36in contact with the poles of the permanent magnet 32 The permanent magnet 32 operates in the nature of a holding means for retaining the latch in engaged position until the centrifugal force is sufficient to overcome the magnetic holding force and other forces noted above whereupon the latch will be released with substantially a snap action. It will also be seen that the permanent magnet may be used as a means to accurately calibrate the speed of rotation at which the latch will be released by energizing the magnet to different extents to vary the flux produced by the magnet. On release of the latch 26, the plunger l8 will, of course, be forced outwardly by spring 20 to engage the several contacts til as shown in Fig. 4 and thereby complete a current path from these contacts connected to the ignition circuit to the contact connected to ground by strap 52 to shortcircuit the ignition system. It will also be apparent that after the engine has stopped or the speed of shaft 6 lowered to below the predetermined safe limit above which the latch is released, the plunger l8 can be reset to its retracted position by the reset member 69. v I

Although shown and described hereinin connection with a switch arrangement adapted for use as an overspeed engine cutout, it will be understood that certain features of the present construction are obviously adapted for use in other types of centrifugal switches, and that such features as the provision of a holding magnet may be used in either centrifugal switches or in other.

forms of centrifugal devices wherein it is desired to operate a member in responseto centrifugal force at some predetermined speed of rotation.

Many modifications and changes in the construction shown and described herein will also be apparent'to those skilled in the art and are contemplated as coming within the scope of the present invention as defined in the claims appended hereto.

I claim: w

1. In a centrifugal switch, the combination of a rotatable shaft, a spring-pressed circuit operating means on said shaft, a centrifugally-operated latch mounted on said shaft adapted to normally engage and hold said means in retracted position, and magnetic means cooperating with said latch adapted to modify the action of the centrifugal force tending to release said latch on rotation of said shaft. 1

mally engage and hold said means in retracted position. and magnetic means mounted on said shaft and cooperating with said latch, said magnetic means tending to retain said latch in engagement with said circuit operating means in opposition to the centrifugal forcetending to release said latch on rotation of said shaft.

3. In a centrifugal switch, the combination of a rotatable shaft, 2. spring-pressed circuit operating means on said shaft, a latch mounted on said shaft and adapted to normally engage and hold said means in retracted position but to be released by centrifugal force on rotation of said shaft, and magnetic means adapted to retain said latch against release below some predetermined speed of rotation of said shaft.

4. In a centrifugal switch, the combination of a rotatable shaft, a spring-pressed circuit operating means on said shaft, a. centrifugally-operated latch mounted on said shaft adapted to normally engage and hold said means in retracted position, a permanent magnet mounted on said shaft, and an armature associated with said latch adapted to be positioned in the magnetic field of said magnet when said latch is in engagement with said circuit operating means.

5. An automatic cutout device for an engine ignition system comprising a movable contact member, means for moving said contact member into cutout position, a latch device for retaining said member in non-cutout position, dual means tending to retain said latch device in latched position, and means acting by centrifugal force to withdraw said lat-ch device from latched position.

6. An automatic cutout device for an engine ignition system comprising a movable contact member, a magnetic means and a spring means acting together to normally retain said movable contact member in non-cutout position, means urging said member toward cutout position, said magnetic means and said spring means being 2. In a centrifugal switch, the-combination of calibrated to be overcome by a predetermined centrifugal force acting in opposition to them to thereby release said member from its retained position, and manually operated means for restoring said movable contact member to noncutout position.

7. An automatic cutout device for an engine ignition system comprising a movable contact member,a magnetic means and a spring means for normally retaining said movable contact member in non-cutout position, said magnetic means and said spring means being calibrated to be overcome by a predetermined releasing centrifugal force acting in opposition to them, and a means for manually restoring said movable contact member to non-cutout position.

8. An interrupter device for an engine ignition system comprising an engine rotated carrier, a grounded contact member movably mounted on the carrier, means urging the member into interrupting relation with the system, an armature latch mounted on the carrier and operable to engage the member and restrain movement thereof into such interrupting relation, and a permanent magnet mounted on the carrier and exerting a magnetic force sufiicient to hold the armature latch in restraining relation with the contact member, said armature latch being movable away from the contact member in response to centrifugal force at a predetermined speed of the carrier.

9. A contact device for an electric system comprising a stationary contact member, a rotating carrier, a movable contact member on the carrier,

means urging the movable contact member into contact with the stationary contact member, a latch restraining the movable member, centrifugal operating means to move said latch to non-restraining position, and a permanent magnet mounted on the carrier in relation to the latch tending to hold the latch in restraining position and against the action of the centrifugal means.

10. An automatic cutout device for an engine ignition system comprising a movable contact member, means for moving said contact member into cutout position, a latch device for retaining said member in non-cutout position, magnetic means and spring means tending to retain said latch device in latched position, and means act- 15 ing by centrifugal force to withdratv said latch device from latched position.

VAUGHN H. HARDY. REFERENCES cI'rEn The following references are of record in the file of this patent:

UNI'I'ED S'I'A'I'ES PATENTS 10 Number Name Date 2,215,294 Morrill Sept. 17, 1940 2,344,867 Heintz Mar. 21, 1944 2,368,567 Philo Jan. 30, 1945 2,432,699 Taylor Dec. 16, 1947 

